1. Field of the Invention
The present invention relates to the field of control devices of motors to be used for copying machines or the like, and typically to motor control devices suitable for use in copying machines for performing continuous size change through continuous control of the speed of the scanning optical system.
2. Description of the Prior Art
In this type of control unit, particularly in the PLL control, the PLL control characteristics have been dependent on the characteristics of the low-pass filter.
In addition, in a control device designed to synchronize with the speeds which are various set points, it has been required that the above low-pass filter should be switched.
In addition, for the PWM (pulse width modulation) of the motor, devices such as an adder for the addition of a PLL signal and a speed control loop signal and an integrator for integrating the adder output have been required.
In addition, since these, in general, devices, have been comprised of hardware, the reference frequency and feedback frequency from the encoder of the driving motor have been divided by a divider for continuous speed change or the reference frequency has been switched with th inevitable increase of the device size as a drawback.